The present invention relates to an improvement of various cameras such as a lens-fitted photographic film unit, a simplified camera, a single-lens reflex camera, a video camera and a camera for measuring instruments.
In general, a camera (still camera, lens-fitted photographic film unit, video camera etc.) is equipped with various control means for controlling appropriately photographing conditions such as exposure, a focusing position and magnification (zooming). The control means of this type is required to have a mechanism capable of realizing precise and complicated functions for an improvement of camera performance. On the other hand, however, it is desired that the mechanism mentioned above is omitted or the mechanism is of a simple structure for the purpose of preventing an increase in weight of a camera main body, complicated assembly steps and cost increase.
In a lens-fitted photographic film unit which has come into wide use recently, in particular, it is preferable that these control means are simplified as far as possible. For this reason, therefore, lens-fitted photographic film units which are available on the market are mainly of a fixed exposure system having no aperture-adjusting mechanism. In this case, a fixed exposure of the camera is set fixedly to the condition wherein over exposure tends to be prior to under exposure with an assumption that the camera may be used also for indoor photographing under less quantity of light. This is based on the fact that a photographic film generally has a characteristic that latitude (recording and reproducing power of a film) of the film is wider in an over exposure region than in an under exposure region.
In the case of ordinary photographing such as those for snapshots, over exposure is caused in not a few photographing locations such as the bright outdoors in summer or ski slopes. Therefore, a lens-fitted photographic film unit equipped with an aperture-adjusting mechanism which is light in weight, small-sized and inexpensive is desirable. However, the aperture-adjusting mechanism has many problems of cost increase such as that the structure is complicated and a motor for driving various movable parts including aperture blades is needed. Accordingly, nothing has been realized as a product.
For the same reason as in the foregoing, most of lens-fitted photographic film units and low-priced cameras employ a fixed focus system which does not have an automatic focusing mechanism, Namely, in a dominating camera, an object in the standard position established to be several meters ahead of the camera and those located before and behind the object to be within the depth of field of the camera can be in focus while those in the region (close distance and long distance) other than the foregoing are out of focus. In the case of typical souvenir photographs on the subject of figures and scenery, the fixed focus has its own utility. Due to the low price thereof, a camera wherein better focus condition can be selected has been desired strongly. However, an automatic focusing mechanism requires a mechanism that is equal to or higher than that for the aforementioned aperture-adjusting mechanism on the point of precision and complexity. Therefore, a low-priced lens-fitted photographic film unit provided with a function of this kind has not been realized yet.
For the reason that is exactly the same as above, mechanisms for zooming, automatic film-winding and self timer are not employed in a lens-fitted photographic film unit, and sharp simplification of these mechanisms also for an ordinary camera has been required.
In the conventional camera mentioned above, the biggest problem in simplifying mechanisms for aperture-adjusting and focusing has been lying in a motor which needs to be used as a driving source. Namely, an ordinary electric-powered motor is equipped with a stator provided with a coil for generating a magnetic field and a rotor that is rotated by an interaction with the magnetic field. Therefore, the motor is heavy, the space occupied by the motor is large and the price of the motor is high, which have been disadvantages. This also applies exactly to a direct operated linear motor. A supersonic motor developed recently is light in weight because no coil is used therein. However, it is expensive and it requires precise assembling. Therefore, it has been extremely difficult to use it in a simplified camera such as a lens-fitted photographic film unit.
With a background mentioned above, an object of the invention is to provide a camera equipped with a stop, a focusing mechanism, a zooming mechanism, a automatic film-winding mechanism, a self timer and a shutter all made up of means which are extremely simple and inexpensive.